THX® stands for Tom Holman eXperiment (or is it named after George Lucas' first film "THX 1138"?), which came about when GL went to cinemas after the theatrical release of Star Wars, and discovered that the sound that he had so carefully crafted for his film was often ruined by poor sound systems in cinemas. This led to the idea of certifying cinemas that took the trouble to provide decent sound. Testing involves checking background noise levels, dispersion of sound within the theatre, maximum sound pressure levels (SPLs), and distortion levels.
For home users, THX® can bring mixed blessings. The processing itself adds three additional processes. A filter cuts treble output from the centre channel. This is because in theatres, a treble boost is applied to compensate for the fact that the speakers are located behind the screen, cutting treble levels. The second process is called timbre matching. This compensates for the way that we perceive sounds differently depending on whether they come from in front, to the side or behind us. The final process is de-correllation. This takes the mono signal supplied to the two rear speakers, aand by various processes, including phase and pitch alterations, de-localises the signal coming from the two rear speakers, getting away from the very directional sound from the rear in conventional pro-logic set-ups. These effects combine to give a greatly enhanced sense of spaciousness, and a more enjoyable cinematic experience.
THX® power amps, although giving guaranteed output levels and low distortion, do not necessarily give wonderful sound, especially with music. As with most hi-fi amps, there are both good and bad examples. The one thing that you can be sure of is plenty of power!
THX® speakers are ideal if your system is going to be used only for playing theatrical material. If one is going to play music through the system as well, I personally would look at conventional speakers.Some manufacturers, in my experience KEF and Linn Products being the best two, manufacture speakers capable of superb performance with both films and music.
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